1886.] 



Effects of Stress and Magnetisation on Iron. 



247 



been loaded strongly and then unloaded down to a certain constant 

 state of stress, and, on the other hand, when the same state of stress 

 has been produced by simply increasing the load ; and it is shown that 

 these residual effects are wiped out by vibration or by demagnetising 

 by reversals. With regard to the effect of stress on thermoelectric 

 quality, it is shown that if a somewhat soft wire be more and more 

 strongly magnetised, these effects become more and more similar to 

 those which are found when the wire is hard drawn, but not magnet- 

 ised. A few experiments were made with wires of silver, copper, 

 lead, magnesium, and German silver, but in none of these was 

 hysteresis of thermoelectric quality with regard to load discovered. 



Special attention is directed to a peculiar feature in the carves by 

 means of which the experimental results are exhibited. In curves 

 showing the relation of thermoelectric electromotive force to load, it 

 is shown that any reversal from loading to unloading, or vice versa, 

 causes an inflection in the curve, the first effect of the new process 

 being to continue the kind of change that was going on before. That 

 this is not due to any mechanical disturbance which the loading or 

 unloading produces, is shown by the fact that it occurs in an equally 

 marked way after the molecules have been brought to a condition of 

 stable equilibrium by vibrating the wire before beginning to load or 

 unload. It is suggested that the effects of hysteresis, described in the 

 paper, have a possible relation to the properties which Professor 

 Osborne Reynolds has recently shown to be possessed by granular 

 media. 



The experiments described in the paper ; are closely connected with 

 those which were communicated in January, 1885, under the title 

 "Experimental Researches in Magnetism," and are now being pub- 

 lished by the Society. They were conducted in the Physical Labora- 

 tory of the University of Tokio, in 1881-3, partly with the help of 

 one of the author's Japanese students, Mr. P. S. Sakai. The results 

 are given graphically, and are for the most part reduced to absolute 

 measure. 



